The present invention relates to a method for cleaning stony surfaces and the like, with a low or small environment impact.

As is known, the interaction of chemical compounds or elements, as generated by modern activities, and discharged into the atmosphere, provides conditions favoring degradation phenomena, of a sulphation and/or carbonation type, depending on the active principles comprising sulphur dioxide and carbon dioxide, in combination with oxygen of air and rainwater.

Of the air-conveyed particle material depositing on exposed surfaces, both of a horizontal or of a vertical arrangement, sulphur dioxide is the main responsible of urban and historical degradation.

Moreover, it is also known that all stony materials have a specific porosity.

Because of mechanical stresses, such as, for example, urban traffic, microcracks are generated which, during icing and thawing cycles, because of an expansion and shrinking action, increase the thickness and depth of the mentioned microcracks.

Thus, it should be pointed out that the above mentioned continuous action in a nearly unstoppable manner, thereby producing degradation phenomena, such as darkenings, non natural pigmentations, plaster and reinforcing iron explosions, vegetable colony formations and chalking.

Moreover, the atmospheric environment further comprises solid particle materials such as silicas, crystal sands and so on, subjecting the surfaces to an abrading action, with a consequent erosion of the exposed materials, which loose their surface resistance starting characteristics.

Another cause of the above mentioned degradation is that of social situations such as wordings, murales and soilings, which, because of different reasons, cause serious consequences, such as artistic work damagings and a consequent decay of urban zones in general.

At present, the cleaning is conventionally performed by mechanical or chemical types of methods.

In particular, a mechanical cleaning method provides to use abrasive wheels, sanding machines, hydrosanding devices, hydrocleaners, carbon dioxide apparatus.

The above mentioned prior systems, if properly used, achieve the objective of properly cleaning the affected surface, but they are affected by intrinsic operation defects, such as an abrasion of the stony matrix which, very frequently, for common stoning materials used for coating facades, would increase natural porosity and microcrackings, thereby accelerating a degradation of the surface to be protected.

Chemical cleaning systems or methods, on the other hand, conventionally provide to use interacting paint removing and cleaning materials, mainly consisting of solvents and surface active agent mixtures, which, mainly because the presence of the solvent, make difficult to properly control the environment ejection, thereby they cannot be used in a free environment and without a recovery possibility.

Moreover, the presence of organic compounds can originate undesired actions inside the stony object, thereby changing the original composition thereof.

Thus, the aim of the present invention is to overcome the above mentioned problem, by providing a method for cleaning stony surfaces and the like, with a low environment impact, allowing to associate mechanical and chemical activities, thereby preventing any environment impact deriving from an use of dangerous volatile products.

Within the scope of the above mentioned aim, a main object of the present invention is to provide such a cleaning method which does not mechanically damage the surfaces being processed because of abrasion phenomena.

Another object of the present invention is to provide such a cleaning method requiring a small operating power with a very reduced environment impact deriving from noise and used products, thereby said method can be carried out without the need of taking specific application protective measurements.

Another object of the present invention is to provide such a cleaning method which, owing to its specifically designed features, is very reliable and safe in operation.

Yet another object of the present invention is to provide such a cleaning method which can be easily carried out and which, moreover, is very competitive from a mere economic standpoint.

According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a method for cleaning stony surfaces and the like with a low environment impact, characterized in that said method comprises the step of ejecting, at a low pressure, on a surface to be processed a water and sodium bicarbonate solution to provide a physical-chemical action suitable to remove atmospheric particle materials, paint layers and mass deposits, such as alimentary gums.

Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed disclosure of a preferred, though not exclusive, embodiment of a method for cleaning stony surfaces and the like, with a low environment impact, which is illustrated, by way of an indicative but not limitative example, in the accompanying drawings, where:

• Figure 1 shows a diagram of the system used for carrying out the cleaning method according to the present invention;
     and
• Figure 2 schematically shows the delivery nozzle for delivering the cleaning product.

With reference to the number references of the above mentioned figures, the method for cleaning stony surfaces and the like, with a low environment impact, comprises the step of ejecting, at a low pressure, on the surface to be processed, a water and sodium bicarbonate solution, thereby providing a physical and chemical action suitable to remove atmospheric particle materials, paint layers and mass deposits such as alimentary gums and the like.

More specifically, it is possible to use, in addition to very pure sodium bicarbonate, at 99%, of suitable particle size, a sodium bicarbonate, calcium carbonate and magnesium carbonate mixture or blend.

According to a further approach, it is possible to use a sodium bicarbonate, iron oxide mixture including an amount less than 0.16% of F₂O₃, calcium carbonate and magnesium carbonate.

Another mixture which could be used would comprise sodium bicarbonate, calcium carbonate, magnesium carbonate and silica oxide in an amount less than 0-1%.

A further mixture which could be used, and having a controlled particle size, would comprise mineral materials free of silica and quartz, in particular calcium and magnesium compounds.

As is shown in figure 1, for conveying and ejecting the powders, which are held in a powder tank 1, a taking nozzle 2 is provided, forming a Venturi element, thereon is coupled an air delivery branch 3, having a main branch 4 communicating with a delivery nozzle 10 to which is further connected the powder inlet duct 11.

Downstream of the Venturi tube formed by the nozzle 10, a mouth or inlet 12 is moreover provided for supplying water at a hydraulic system pressure, so as to provide a solution or mixture, depending on the type of the used material.

The oversaturated solution or mixture, at the outlet of the nozzle, will immediately loose the acquired propelling power, with a comparatively high reduction of the stony matrix, on which the cleaning product is ejected.

Thus, with the above disclosed arrangement, the decreasing cleaning effect typical of bicarbonate will be held up to the end of the final washing and, at the end of the cleaning operations, on the cleaned and dried surface two layers of protecting product will be applied.

Said protecting products are generally based on paraffins or fluorine resins and are typically made depending on their particular application.

In particular, on vertical surfaces it would be possible to use an anti-wording protective product, i.e. a fluorine resin aqueous solution, suitable to facilitate the removal of the vandalic wordings.

The product does not form films, does not change the color of the processed surface and allow the support to transpire with respect to the water steam, and moreover it also has good waterproofing characteristics.

The product would be of a sacrificial type, since, in removing the wordings, also a protective layer is removed which, however, could be reapplied after the cleaning operation.

Another protective product would comprise a paraffinic wax aqueous emulsion which, after application, will form a film on the coating surface, and, upon drying the film, will allow to obtain very good waterproofness properties without altering the transpiration capability.

This product would allow to achieve a better water resistance and, moreover, will prevent atmospheric powder or dirt to adhere, which would frequently deteriorate the film aspect.

Moreover, the latter is also adapted to greatly facilitate the removal of the vandalic wordings.

Yet another specific protective product, for horizontal surfaces would comprise fluorine resin dissolved in a solvent.

Such a product does not form films and change the support color, and moreover has very good waterproofing and oilproofing characteristics, and is adapted to greatly facilitate the removal of alimentary gums and soil in general.

For removing paints from the surfaces being processed, a paint removal product will be used, comprising a biodegradable cleaning component, to be applied by spraying or by padding and which could be reapplied in a case of a difficult to be removed wording.

From the above disclosure it should be apparent that the invention fully achieves the intended aim and objects.

In fact, the invention provides a method for cleaning stony surfaces and the like with a low environment impact which, by combining a mechanical action and chemical action, allows to overcome all the drawbacks of the prior art, by providing a very satisfactory cleaning of the surfaces being processed, without abrading them, but carrying out a very efficient and delicate removal.

The invention, as discloses, is susceptible to several modifications and variations, all of which will come within the scope of the invention.